1. Field of the Invention
The present invention relates to a connecting structure for an indicator display, and particularly, the number of electric wires forming a wire harness for connection is reduced to a single wire, by improving the inhibitor switches of an automatic transmission and a gear indicator.
2. Description of Background Information
Many automotive vehicles have an automatic transmission include a gear position indicator on a vehicle information display, which is provided with a speedometer, various kinds of warning lamps, and the like, for communicating the present gear position to a driver.
FIG. 2 schematically shows wiring for indicating the gear position of an automatic transmission in a vehicle. The automatic transmission 3 connected with an engine 2 installed in an engine compartment 1a of a vehicle 1 includes an inhibitor switch that judges a gear position. The inhibitor switch 4 provides a gear position signal and is connected by a wire harness W/H with a gear indicator 6 of a vehicle information display 5 which is provided in an instrument panel and the like.
FIG. 3 shows a conventional connection circuit for indicating the above-mentioned gear position. The automatic transmission 3 of the present conventional example has a total of six positions including parking P, reverse R. neutral N, drive D, a second speed fixation {circle around (2)}, and a first speed fixation {circle around (1)}. The inhibitor switch 4 constitutes an inner circuit by a first circuit to a sixth circuit 7a to 7f having contact points 4a to 4f for the respective positions at ends which correspond to the above-mentioned six positions, and has a contact piece 4g which is linked to the gear position of the automatic transmission 3.
The inhibitor switch 4 is connected by the wire harness W/H with the gear indicator 6 including the display lamps 6a to 6f which correspond to the respective positions of P, R, N, D, {circle around (2)} and {circle around (1)}. Since the wire harness W/H directly corresponds to and connects respectively the signal out-put parts 8a to 8f of six points, such as the first circuit to the sixth circuit 7a to 7f of the inhibitor switch 4, with the signal in-puts 9a to 9f of six connection points of the gear indicator 6, the wire harness is configured to have six electric wires d1 to d6 and also includes the connectors C1 to C4 for connection.
The display of the respective gear positions are described below.
When a power source of the vehicle 1 is turned on, the contact 4g of the inhibitor switch 4 is connected with the power source and closes the contact point corresponding with the gear position of the automatic transmission 3. The power source V then sends out a signal of the gear position through the wire harness W/H, and a corresponding display lamp is lighted.
In the wire harness W/H formed by the above-mentioned six electric wires d1 to d6, when one of the display lamps is lighted, only one of the electric wires is used for signal transmission, and the other electric wires are unused, which results in a surplus of wires from the standpoint of a circuit. Further, in order to prepare the wire harness W/H containing the six electric wires d1 to d6, the expenditure of six electric wires is thus required, as well as six terminals installed on each end of the electric wires. Further, the connectors C1 to C4, having a size sufficient to accommodate the six electric wires, are also required, and the wire harness W/H must be assembled with the six electric wires. Accordingly, the assembly is time consuming and requires a number of parts, and the result is that the assembly of the wire harness W/H is expensive. Further, when the number of electric wires become plural, the number of connection points and the like increase, and there is a concern that connection problems and the like will also increase corresponding to the number of electric wires.
Further, there conventionally exists a so-called multiple system unit which carries out various kinds of signals with one electric wire by respectively making the frequencies of transmission signals different. However, when the multiple system unit is applied to the display circuit of above-mentioned gear position, it is necessary that an expensive frequency converter is provided on the inhibitor switch at the signal out-put side, and a discriminator that discriminates the respective signals having different frequencies is provided on the gear indicator at the signal in-put side. Accordingly, a reduction of costs is not achieved, and an installation space for these devices must be provided.
The present invention was developed considering the above-mentioned problems, and an object is to reduce the number of electric wires used for the connection to a single wire. A further object is to reduce costs by respectively making the electric current value of signals output from the inhibitor switch different, without using a multiple system unit.
In order to solve the above-mentioned problems, the present invention provides a connecting structure for an indicator display connecting an inhibitor switch that outputs signals corresponding to respective gear positions connected by a wire harness with a gear indicator for indicating the gear positions by the input of the above-mentioned signals which is provided in a vehicle information display in a passenger compartment.
The connecting structure includes the output circuit of the inhibitor switch having a plurality of circuits with different resistance values for each respective gear position, and a signal output is formed by collecting the end of the output side of the plurality of circuits. A judgment circuit that discriminates and judges electric current values through a single signal input part is provided in the gear indicator.
The signal output of the inhibitor switch and the signal input of the gear indicator are connected with a wire harness, and the gear position is indicated by the gear indicator.
Thus, the electric current value of a signal output from the inhibitor switch can be made different by respectively making the resistance values of the respective circuits corresponding to the respective gear positions of the inhibitor switch different. Further, the signal output of the inhibitor switch and the signal input of the indicator become one position, respectively, by providing a judgment circuit that measures the electric current values of the signals and carries out the opening and closing of the circuits of respective display lamps in accordance with corresponding electric current values, and the electric wire that forms the connection can be a single electric wire.
Namely, even if the inhibitor switch and the gear indicator are connected by a wire harness W/Hxe2x80x2 constituted by a single electric wire and the signals of the gear positions are transmitted by that electric wire, the electric current values of the signals differ due to the difference resistance. Thus, the signals can be judged simply by judging the electric current. Further, the display lamp corresponding to the signal can be illuminated by carrying out the judgment of the electric current values by the judgment circuit provided in the indicator. Accordingly, the wire harness can be formed of only a single electric wire. Thus, the expense required for the wire harness can be reduced.
Further, since the difference of the resistance values of the respective circuits can be realized by only building the resistances having different resistance values in the respective circuits, it can be corresponded more easily and at a far lower cost, as compared with that of the frequencies of the respective signals that are made different as a multiple system unit. Further, as the signal input only judges the difference of the electric current values, various kind of signals can be positively discriminated without additional expense, as compared with signals judged by the difference of the frequencies of the multiple system unit.